The present invention relates to a fuel pump of a turbine type which is suitably adapted for feeding fuel, for example, to an engine of automobiles.
In general, vehicles such as automobiles are provided with a fuel pump for feeding fuel to an engine thereof. As the fuel pump, there are known fuel pumps of a turbine type in which a disk-shaped impeller is rotatively driven to feed the fuel under pressure.
Japanese Patent Application First Publication No. 6-229388 discloses a fuel pump including a cylindrical casing, an electric motor as a power source for the fuel pump and a rotating shaft coupled to an output side of the electric motor which are accommodated in the casing.
A pump housing is disposed at one end portion of the casing in which a tip end portion of the rotating shaft is located. A suction port, a discharge port and an annular fuel path connected to the suction and discharge ports are defined within the pump housing. An impeller is rotatably disposed within the pump housing and coupled to the tip end portion of the rotating shaft. The impeller is located on an inner circumferential side of the fuel path.
When the impeller is rotatively driven by the electric motor via the rotating shaft, the fuel pump sucks the fuel through the suction port by rotation of the impeller and then delivers under pressure the fuel through the fuel path toward the discharge port.
The impeller is formed into a toothed disk shape, for example, by injection-molding a resin material, and provided at an outer periphery thereof with a plurality of vanes circumferentially spaced from each other. The vanes are arranged within the fuel path when assembled in the fuel pump. The respective vanes project radially outwardly from an annular body of the impeller and are formed into a rectangular plate whose projecting end or tip end has, for example, a pointed shape or an acute-angled shape.
In the thus arranged fuel pump, merely a slight change in, for example, shape, dimension, etc., of the vanes of the impeller gives a considerable influence on efficiency of fuel delivery under pressure by the impeller, i.e., pump efficiency. For this reason, conventionally, in order to form the respective vanes into predetermined shape, dimensions, etc., the impeller must be molded from a resin material at high accuracy with a great care, and an outer peripheral surface of the impeller, namely, the tip end faces of the vanes, as well as opposite faces thereof must be subjected to further mechanical processing.